Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Crosslinking of DNA fibers by histone H1 or phosphorylated on Ser-37 histone H1, and by the individual fragments of the H1 polypeptide chain was studied by the method of turbidimetry. The dependence of the turbidity of DNA-protein complexes on the ionic strength in solution suggests that the condensation of H1.DNA complexes in vitro is apparently due to both specific histone-DNA interactions with the contribution of hydrogen and/or hydrophobic bonds and the formation of polycationic "bridges" fastening the DNA fibers. The effectiveness of the condensation is postulated to be a function of a proportion between the two mechanisms which in turn can be controlled by slight changes in ionic surroundings. The sharp dependence of shrinkage of H1.DNA complexes on ionic strength at "physiological" salt concentrations could provide a mechanism to regulate density and consequently the total activity of chromatin in the cell nuclei. The phosphorylation of histone H1 on Ser-37 by a specific histone kinase does not noticeably affect the pattern of DNA crosslinking by the H1.
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PMID:Histone H1--DNA interaction. On the mechanism of DNA strands crosslinking by histone H1. 2 66

By measuring the fluorescence polarization of fluorescent histone H1 derivatives complexed with DNA, binding of the histone to DNA was studied as a function of ionic strength in the solution prior to and after the H1 phosphorylation on Ser-37 residue. Fluorescent labels were covalently linked either specifically to Tyr-72 residues or unspecifically to lysine residues in the H1 polypeptide chain. The values of the corresponding rotational relaxation times showed that at low ionic strength all the segments of the H1 molecule were immobilized on binding to DNA. The gradual increasing NaC1 concentration in the solution of H1-DNA complex was accompanied at first by additional retardation of the histone mobility in the complex, and then by progressive release of histone H1 from from the complex which was completed at 0.5-0.6 M NaC1 irrespective of phosphorylation. tat the same time the phosphorylation of histone H1 led to removal of the central and, presumably, N-terminal regions of H1 from DNA.
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PMID:Histone Hl-DNA interaction. Influence of phosphorylation on the interaction of histone Hl with linear fragmented DNA. 19 28

Synthetic polypeptides were employed as substrates in kinetic analyses of the reaction mechanism for the catalytic subunit of a cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) from calf thymus. This enzyme preparation was shown to catalyze the transfer of phosphate from ATP to histone H1 from calf thymus, as well as to two synthetic polypeptides, Arg-Lys-Ala-Ser-Gly-Pro (H1-6) and Arg-Arg-Lys-Ala-Ser-Gly-Pro (H1-7), corresponding to the amino acid sequence about serine-38 in calf H1. A related, basic heptapeptide corresponding to a sequence from pig liver pyruvate kinase, Leu-Arg-Arg-Ala-Ser-Leu-Gly (K), was also a substrate. The stoichiometry of peptide phosphorylation was established in each case as the transfer of 1 mol of phosphate from the gamma position of MgATP to the serine hydroxyl of 1 mol of the peptide. Steady-state, initial-velocity, kinetic parameters were determined for each substrate, using various concentrations of ATP. Under the conditions used, all synthetic peptides reacted with greater maximum velocities than whole histone H1. Nevertheless, the K(m) for H1, 54 muM, was lower than the K(m) values of the synthetic substrates. The most efficient substrate was peptide K, which had a V(max) of 50.6 mumol/min per mg of kinase and a K(m) of 63 muM. In the absence of peptide substrate no ATPase activity was detectable at a sensitivity of 0.05% of the rate of peptide phosphorylation, suggesting that ATP is not cleaved to form an unstable phosphoenzyme complex. The data are consistent with a sequential reaction mechanism involving a ternary complex between enzyme, polypeptide substrate, and ATP.
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PMID:Studies on the mechanism of phosphorylation of synthetic polypeptides by a calf thymus cyclic AMP-dependent protein kinase. 20 Sep 11

Yeast chromatin, isolated by a rapid procedure contains in addition to histones H2A, H2B, H3 and H4 a fifth major basic protein. This fifth polypeptide is not an intrinsic component of the nucleosome structure. It has properties of both histone and nonhistone proteins and might represent an early form of histone H1 and of high mobility group nonhistone proteins of higher eukaryotes. Electron microscopic visualization of isolated yeast nucleosomes substaniates further the similarity of the chromatin structudre of this unicellular eukaryote to that of higher eukaryotes.
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PMID:Yeast chromatin: search for histone H1. 35 18

The results in the literature to support Orgel's general error hypothesis of ageing only provide indirect evidence that errors in protein synthesis increase during senescence. This study attempts to provide direct evidence of errors in protein synthesis by measuring the misincorporation of 35S-methionine into histone H1 obtained from young and old fibroblasts (MRC-5). The conclusions that can be drawn from this study are: (a) the error level for the misincorporation of methionine into histone H1 is less than 7 methionines/10(5) amino acids and 2-3 methionines/10(4) amino acids in young and old cells respectively; (b) a methionine containing fraction associated with H1 is obtained after the final purification. The amount of this fraction increases with the age of the cell culture as does the number of methionine residues; (c) there is a variation in the complexity of H1 polypeptide chains, the complexity increasing with the age of cultured cells.
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PMID:Fidelity of histone synthesis in cultured human fibroblasts. 65 92

Functional expression of recombinant wild-type phosphatase 2A catalytic subunit has been unsuccessful in the past. A nine-amino-acid peptide sequence (YP-YDVPDYA) derived from the influenza hemagglutinin protein was used to modify the NH2 and/or COOH terminus of the phosphatase 2A catalytic subunit. Addition of the nine-amino-acid sequence at the NH2 terminus allowed recombinant phosphatase 2A expression as a predominantly cytosolic phosphatase 2A enzyme. The 12CA5 monoclonal antibody that recognizes the nine-amino-acid hemagglutinin peptide sequence was used to immunoprecipitate the epitope-tagged phosphatase 2A catalytic subunit. Assay of the immunoprecipitated epitope-tagged phosphatase 2A demonstrated an okadaic acid-sensitive dephosphorylation of [32P] histone H1 and [32P]myelin basic protein similar to that measured with the wild-type enzyme. Functional phosphatase activity could be demonstrated for the NH2-terminal modified phosphatase 2A catalytic subunit following transient expression in COS cells or stable expression in Rat1a cells. In contrast, the COOH-terminal-modified phosphatase 2A catalytic subunit was very poorly expressed. The NH2-, COOH-modified subunit, having the nine-amino-acid hemagglutinin peptide sequence encoded at both termini of the polypeptide, was also expressed as a functional phosphatase 2A enzyme. Thus, NH2-terminal modification of the phosphatase 2A catalytic subunit results in a functional plasmid-expressed enzyme. The unique nine-amino-acid epitope-tag sequence also provides a method to easily resolve the recombinant phosphatase 2A from the endogenous wild-type gene product and related phosphatases expressed in cells.
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PMID:NH2-terminal modification of the phosphatase 2A catalytic subunit allows functional expression in mammalian cells. 138 Sep 55

The proliferative effects of colony-stimulating factor 1 (CSF-1) on macrophages are exerted only throughout the G1 phase of the cell cycle. Genetic targets of the delayed early response to CSF-1 include novel G1 cyclin (CYL or cyclin D) genes. In macrophages, cyclin D1 is induced early in G1 and is expressed throughout the cell cycle as long as CSF-1 is present. The cyclin D1 protein turns over rapidly in CSF-1-stimulated cells and its level declines precipitously upon CSF-1 withdrawal. Cyclin D2 is induced later in G1 and its expression is periodic, whereas cyclin D3 is not expressed in macrophages but is regulated by growth factors in other cell types. The cyclin D1 protein associates during G1 with a polypeptide antigenically related to p34cdc2 and binds in vitro to a histone H1 kinase present in lysates of CSF-1-starved macrophages. The instability of the cyclin D1 protein and its ability to rescue a cyclin-dependent kinase activity from growth factor-deprived macrophages together suggest that the cyclin D protein is the dynamic partner in the complex. The timing of expression of cyclin D genes suggests that they act to link growth factor signals with cell cycle transitions during G1.
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PMID:Regulation of CYL/cyclin D genes by colony-stimulating factor 1. 148 47

Three serine kinases which phosphorylate the CTD of RNA polymerase II have been identified in Aspergillus nidulans. The kinases (KI, KII, KIII) were identified using a synthetic peptide containing four copies of the CTD consensus heptamer repeat, and differ in chromatographic behavior, and apparent molecular mass (KI approximately 60kDa; KII approximately 82kDa; KIII approximately 43 kDa). KIII utilized, in addition to peptide, histone H1 as substrate, whereas casein was not phosphorylated by any of the three kinases. The kinases appear to be unrelated to the p34cdc2 kinase, as judged by Western blot analysis and the position of serine phosphorylation of the synthetic CTD peptide. KI was highly purified and renaturation experiments have shown that it consists of a single polypeptide of 57 kDa. KI also phosphorylated RNA polymerase II associated in a preinitiation complex.
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PMID:Protein kinases from Aspergillus nidulans that phosphorylate the carboxyl-terminal domain of the largest subunit of RNA polymerase II. 155 38

The nucleotide sequence of the vaccinia virus open reading frame B1 predicts a polypeptide with significant sequence similarity to the catalytic domain of known protein kinases. To determine whether the B1R polypeptide is a protein kinase, we have expressed it in bacteria as a fusion with glutathione S-transferase. Affinity-purified preparations of the fusion protein were found to undergo autophosphorylation and also phosphorylated the exogenous substrates casein and histone H1. Mutation of lysine 41 to glutamine within the conserved kinase catalytic domain II abrogated protein kinase activity on all three protein substrates, supporting the notion that the protein kinase activity is inherent to the B1R polypeptide. Casein and histone H1 were phosphorylated on serine and threonine residues. The B1R fusion protein was phosphorylated on a threonine residue(s) by an apparently intramolecular mechanism. The autophosphorylation reaction resulted in phosphorylation of the glutathione S-transferase portion of the fusion and not the protein kinase domain. The protein kinase activity of B1R was specific for ATP as the phosphate donor; GTP was not utilized to a detectable extent. Immunoblotting experiments with anti-B1R antiserum showed that the protein kinase is located in the virion particle. Chromatography of virion extracts resulted in separation of the B1R protein kinase from the bulk of the total protein kinase activity, indicating that multiple protein kinases are present in the virion particle and that B1R is distinct from the previously described vaccinia virus-associated protein kinase.
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PMID:The vaccinia virus B1R gene product is a serine/threonine protein kinase. 156 May 22

Monoclonal antibodies directed against four different polypeptide epitopes on the Mr approximately 94,000 steroid-binding subunit of the rat liver cytosolic glucocorticoid receptor (GcR) were used to probe Western blots of epididymal spermatozoa from rats and mice. Two sperm polypeptides with apparent molecular weights of 94,000 (indistinguishable in size from the liver GcR subunit) and 150,000 reacted with these antibodies. Other polypeptides that are present in a wide variety of somatic cells [lamin-A, -B, and -C; topoisomerase-I; poly(ADP-ribose) polymerase; the 62-kilodalton internal nuclear matrix protein; the nucleolar protein B23; and histone H1] could not be detected in these preparations of spermatozoa, thus appearing to rule out contamination by somatic cells. Rat and mouse pachytene spermatocytes and round spermatids contained much lower amounts of the Mr approximately 94,000 and 150,000 polypeptides. These results suggested that the steroid-binding subunit of the GcR might be accumulated late in spermatogenesis. Consistent with this view, a 6-kilobase mRNA (identical in size to a mRNA detected in mouse somatic cell lines) was detected when Northern blots of mouse round spermatid RNA were probed with a cDNA to the steroid-binding GcR subunit. Although the results described above suggest the presence of GcR in rodent sperm, high affinity binding of glucocorticoids to epididymal sperm could not be detected in a whole cell binding assay. Further analysis revealed that the Mr approximately 90,000 heat shock protein (hsp90), a component reportedly required for high affinity ligand binding to the GcR, was present in early germ cells, but absent from rodent epididymal sperm. These results suggest that the Mr approximately 94,000 steroid-binding subunit of the GcR and an immunologically related Mr approximately 150,000 polypeptide are specifically accumulated during the later stages of rodent spermatogenesis, but are not assembled into receptor complexes capable of binding steroid. In addition, these results support the view that hsp90 is required for high affinity binding of glucocorticoids to the Mr approximately 94,000 GcR subunit in intact cells.
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PMID:Evidence that rodent epididymal sperm contain the Mr approximately 94,000 glucocorticoid receptor but lack the Mr approximately 90,000 heat shock protein. 157 14


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